Diprotodonts have spread into great variety of ecological niches left open by the absence of placental mammals. A large number are arboreal, and several species have evolved a method of "gliding" from tree to tree. At the opposite extreme are the macropods, which have filled the roles of large grassland herbivores, analogous to the wildebeest of Southern Africa. For awhile, there was even a diprotodont carnivore.